System and method for monitoring the performances of a cable carrying a downhole assembly

ABSTRACT

The disclosure relates to a method for monitoring the performances of a cable for carrying a downhole assembly in a wellbore, the cable having at least a conductive core and an insulating outer layer, the method including:
         performing on the cable a detection operation for detecting the presence of local anomalies of the cable;   generating an electrical model of a predetermined configuration of an installation including the cable and the downhole assembly disposed in the wellbore, the model being defined in function of the detected local anomalies,   estimating a parameter relative to a signal transmitted by the cable between the downhole assembly and a surface equipment in the predetermined configuration on the basis of the electrical model.

BACKGROUND

The disclosure relates to a method for monitoring the performances of acable comprising at least a conductive core and an insulating outerlayer for carrying a downhole assembly in a wellbore.

Electrical performances of cables such as slickline cables are indeed aninteresting parameter to monitor as the communication between thesurface and the downhole assembly greatly depends of the electricalintegrity of the cable, each current leak on the cable generating asignal loss that may lead to a failure of the operation planned for thecable.

Methods for verifying the electrical performances of cables are alreadyused during the build-up of the cable or, as disclosed in patentapplication US2013/141100, at the well site.

SUMMARY

The disclosure relates to a method for monitoring the performances of acable for carrying a downhole assembly in a wellbore, the cable having aconductive core and an insulating outer layer. The method comprisesperforming on the cable a detection operation for detecting the presenceof local anomalies on the cable, generating an electrical model of aconfiguration of an installation including the cable and the downholeassembly disposed in the wellbore, in function of the detected localanomalies, and estimating a parameter relative to a signal transmittedby the cable between the downhole assembly and a surface equipment inthe configuration of the wellbore on the basis of the electrical model.

Such a method gives data in order to predict if a job in differentconfigurations of the wellbore will fail or will succeed. The use of theslickline cable may then be adapted to the performances that the cableis able to deliver.

The disclosure also relates to a system for monitoring the performancesof a cable for carrying a downhole assembly in a wellbore and comprisinga conductive core and an insulating outer layer. The system comprises adetection apparatus for detecting the presence of local anomalies on thecable and a processor for generating an electrical model of aninstallation including the cable and the downhole assembly disposed inthe wellbore, defined in function of the detected local anomalies, anddetermining a parameter relative to the signal transmitted by the cablebetween the downhole assembly and a surface equipment of theinstallation in the configuration on the basis of the electrical model.

The disclosure also related to a sleeve for spooling a cable around adrum, having an cylindrical shape and configured to be disposed around aspooling surface of the drum, the sleeve comprising at least twoindependent parts, each of cylindrical shape and having a first portion,comprising at least a peripheral groove to receive the cable, and asecond portion situated at one of the longitudinal ends of the part andhaving a longitudinal attachment edge. The attachment edges areconfigured so that a longitudinal attachment edge of a first part is ofcomplementary shape of a longitudinal attachment edge of a second part.The attachment edges comprise at least an edge portion, and are eachconfigured so that the total length of the edge portions having atangent situated in a predetermined plan perpendicular to the axis ofthe cylinder are less than 20% of the perimeter of the sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is a schematic view of a intervention installation, comprising asystem according to an embodiment of the disclosure,

FIG. 2 is a schematic view of a first detection apparatus of a systemaccording to an embodiment of the disclosure,

FIG. 2B is a perspective view of a variant of the first detectionapparatus of FIG.

FIG. 3 is a plot showing a signal obtained from the first detectionapparatus shown in FIG. 2 when a cable with a conductive core and anouter insulation layer passes in the first detection apparatus,

FIG. 4 is an schematic drawing representing an electrical model of thefirst detection apparatus and the cable when an anomaly in the cablepasses in the detection apparatus,

FIG. 5 is a schematic view of a second detection apparatus according toanother embodiment of the disclosure,

FIG. 5B is a schematic view of a third detection apparatus according toanother embodiment of the disclosure,

FIG. 5C is a section view of the third detection apparatus of FIG. 5B,

FIG. 6 is a flow diagram of a method for monitoring the performances ofthe cable according to an embodiment of the disclosure,

FIG. 7 is a schematic drawing representing an electrical model of thewellbore generated by a method according to an embodiment of thedisclosure,

FIG. 8 is a plot showing a prediction of a transmitted signal estimatedvia the method of FIG. 6 in a predetermined configuration of theinstallation, versus transmitted signals to and from the surface in saidconfiguration;

FIG. 9 is a representation in perspective of a first embodiment of aspooling sleeve according to the disclosure;

FIG. 10 is a sectional view of a part of the spooling sleeve of FIG. 9situated on a spooling drum,

FIG. 11 is a representation in perspective of a second embodiment of aspooling sleeve according to the disclosure;

FIG. 12 is a sectional view of a part of the spooling sleeve of FIG. 11situated on a spooling drum,

FIG. 13 is a representation in perspective of a variant of the secondembodiment of a spooling sleeve according to FIG. 11.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will bedescribed below. These described embodiments are examples of thepresently disclosed techniques. Additionally, in an effort to provide aconcise description of these embodiments, some features of an actualimplementation may not be described in the specification. It should beappreciated that in the development of any such actual implementation,as in any engineering or design project, numerousimplementation-specific decisions may be made to achieve the developers'specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would still be a routineundertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present disclosure are notintended to be interpreted as excluding the existence of additionalembodiments that also incorporate the recited features.

An intervention installation 10 according to the disclosure isillustrated in FIG. 1. This installation 10 is intended to performoperations in a fluid production or injection well 12 made in thesubsoil 14.

These operations are applied by means of a downhole assembly 30 forcarrying out actions and/or perform measurements at the bottom of thewell 12, such as perforations, cuttings by means of a torch, cementationoperations, jarring operations or further operations for setting toolsinto place such as setting into place a seal gasket or anchoring of atool.

These interventions are carried out in any point of the well 12, fromthe surface 16.

The fluid produced in the well 12 is for example a hydrocarbon such aspetroleum or natural gas and/or another effluent, such as steam orwater, the well is an “injector” well into which liquid or gas isinjected. The production tubing may contain one or several differenttypes of fluid.

The well 12 is made in a cavity 18 positioned between the surface 16 ofthe ground and the fluid layer to be exploited (not shown) located indepth in a formation of the subsoil 14.

The well 12 generally includes an outer tubular duct 20, designated bythe term of “casing”, and formed for example by an assembly of tubesapplied against the formations of the subsoil 14. The well 12 may alsoinclude at least one inner tubular duct 22 with a smaller diametermounted in the outer tubular duct 20. In certain cases, the well 12 iswithout any duct 20, 22.

The inner tubular duct 22 is generally designated as “productiontubing”. It is formed with a metal assembly of metal tubes. It is wedgedinside the outer tubular duct 20 for example by linings 24.

The well 12 includes a well head 26 at the surface which selectivelycloses the outer tubular duct 20 and said or each inner tubular duct 22.The well head 26 includes a plurality of selective access valves insidethe outer tubular duct 20 and inside the inner tubular duct 22.

The intervention installation 10 includes an intervention devicecomprising an intervention and measurement downhole assembly 30 intendedto be lowered into the well 12 through the inner tubular duct 22, and aconveying cable 32 for deploying the downhole assembly 30 in the well12.

The intervention installation 10 further includes a sealing andalignment assembly 34 of the cable 32, mounted on the well head 26, anassembly 36 for deploying the cable 32, positioned in the vicinity ofthe well head 26, and a surface control unit 38.

The sealing and alignment assembly 34 comprises an airlock 42 mounted onthe well head 26, a stuffing box 44 for achieving the seal around thecable 32 and return pulleys 46 respectively attached on the stuffing box44 and on the well head 26 in order to send back the cable 32 towardsthe deployment assembly 36.

The airlock 42 is intended to allow introduction of the downholeassembly 30 into the well 12.

The stuffing box 44 is capable of achieving a seal around the smoothouter surface of the cable 32, for example via annular linings appliedaround this surface or/and by injecting a fluid between the outersurface and the wall of the stuffing box 44.

In a so-called “open well” or “open hole” alternative, in which there isno casing 20, the assembly 34 is exclusively an assembly for aligningthe cable, without any sealing device.

The deployment assembly 36 includes a winch 37A provided with a drum37B. The winch 37A and its drum 37B are laid on the ground or areoptionally loaded onboard a vehicle (not shown). A spooling sleeve maybe fitted around the drum 37B, as will be described in reference toFIGS. 9 to 13. The winch 37A is capable of winding or unwinding a givenlength of cable 32 for controlling the displacement of the downholeassembly 30 in the well 12 when moving up or down respectively. An upperend 41A of the cable may be attached onto the drum 37B.

The surface control unit 38 comprises a processor unit 48 and a firsttelemetry unit 50 for communicating with devices situated at the wellsite, for instance the winder 37B and the downhole assembly 30, and asecond telemetry unit 52 for communication with computers remote fromthe well site.

The intervention installation further comprises a detection apparatus 54for detecting the presence of at least a local anomaly on the cable. Thedetection apparatus, as the winch or other devices of the wellsite, isconnected to the surface control unit 38, via the first telemetry unit50. Embodiments of the detection apparatus will be described in moredetail in reference to FIGS. 2 and 5.

The downhole assembly 30 comprises a hollow case comprising an operatingassembly 58 comprising one or several measuring module and tools such asjarring tools or perforating tool, capable of being controlled from thesurface by electrical signals transmitted through the cable 32. It alsocomprises a telemetry module 60 for communicating with the surfacecontrol unit 38 via the cable 32. The downhole assembly also comprisescontacting elements 62 for contacting with duct 22 in order to enablecommunication with the downhole assembly. The communication is performedvia known method, such as the one disclosed in U.S. Pat. No. 7,652,592hereby incorporated by reference. In other embodiments, the cable may beconnected to the downhole assembly thanks to a capacitive coupling atthe head of the well as disclosed in application No WO2013/098280 forinstance.

The cable 32 is a cylindrical solid cable having a smooth outer surface40.

The cable 32 extends between an upper end 41A, attached on thedeployment assembly 36 at the surface, in particular on the drum 37B,and a lower end 41B, intended to be introduced into the well 12. Thedownhole assembly 30 is suspended from the lower end 41B of the cable32.

The length of the cable 32, taken between the ends 41A, 41B may begreater than 1,000 m and is notably greater than 1,000 m and comprisedbetween 1,000 m and 10,000 m.

The cable 32 has an outer diameter of less than 8 mm, advantageouslyless than 6 mm.

The cable 32 includes a central metal core, and an insulating outersheath applied around the central core.

The central core is formed by a single strand of solid metal cable,designated by the term “piano wire” and sometimes by the term of“slickline cable”.

The metal material forming the core is for example electroplated orstainless steel. This steel for example comprises the followingcomponents in mass percentages:

-   -   Carbon: between 0.010% and 0.100%, advantageously equal to        0.050%;    -   Chromium: between 10% and 30%, advantageously equal to 15%;    -   Manganese: between 0.5% and 3%, advantageously equal to 1.50%;    -   Molybdenum: between 1.50% and 4%, advantageously equal to 2%;    -   Nickel: between 5% and 20%, advantageously equal to 10%;    -   Phosphorus: less than 0.1%, advantageously less than 0.050%;    -   Silicon: less than 1% advantageously less than 0.8%;    -   Sulphur: less than 0.05% advantageously less than 0.03%;    -   Nitrogen less than 1%, advantageously less than 0.5%.

This steel is for example of the 5R60 type.

The core is solid and homogeneous over the whole of its thickness. Ithas a smooth outer surface.

The diameter of the core is typically comprised between 1 mm and 5 mm,advantageously between 2 mm and 4 mm, and is for example equal to 3.17mm, i.e. 0.125 inches.

The core has a breaking strength of more than 300 daN, and notablycomprised between 300 daN and 3,000 daN, advantageously between 600 daNand 2,000 daN.

The core further has a relatively high electrical linear resistance ofmore than 30 mohms/m, and for example comprised between 50 mohms/m and150 mohms/m.

The core has sufficient flexibility so as to be wound without anysubstantial plastic deformation on a drum with a diameter of less than0.8 m.

The outer sheath or outer insulation layer forms an annular sleeveapplied on the core, over the whole periphery of the core, onsubstantially the whole length of the cable 32, for example on a lengthof more than 90% of the length of the cable 32, taken between its ends41A, 41B.

The outer sheath thus has a cylindrical inner surface applied againstthe central core and a smooth outer surface delimiting the smooth outersurface of the cable 32.

The thickness of the sheath is advantageously comprised between 0.2 mmand 2 mm.

The outer sheath includes a polymer matrix.

The matrix is made on the basis of a polymer such as a fluoropolymer ofthe fluorinated ethylene propylene type (FEP), perfluoroalkoxyalkane,polytetrafluoroethylene (PTFE), perfluoromethylvinylether, or on thebasis of a polyketone such as polyetheretherketone (PEEK) orpolyetherketone (PEK), or on the basis of epoxy, optionally taken as amixture with a fluoropolymer, or further based on polyphenylene sulfitepolymer (PPS), or mixtures thereof.

The polymer matrix may be made in polyetheretherketone (PEEK).

The outer sheath optionally comprises mechanical reinforcement fibresembedded in the polymer matrix.

The cable that has been disclosed is a slickline cable but the methodand installation of the disclosure could also be applied on other typesof cables, such as wireline cables, having several conductive elementsforming the conductive core or a cable having several insulating layerswith interposition of conductive layers. The installation is not limitedeither to the one disclosed in FIG. 1.

The quality of the telemetry signals depends directly from theinsulation of the conductive core of the cable and then of themechanical state of the cable and in particular of the outer sheath orinsulation layer. It is therefore interesting to be able to detect theanomalies on the cable in order to predict if a signal will be properlytransmitted to the downhole assembly and, consequently, if anintervention job will be completed or will fail. The anomalies aremainly cracks and holes in the outer insulation layer of the cable thatmay lead to current leaks outside of the conductive core.

The manipulation of the cable for preventing it to be damaged is alsoimportant for decreasing the number of the anomalies on the cable.

A first type of detection apparatus 100 is represented on FIG. 2. Itcomprises a box 101, comprising a first opening 102 forming an inlet forthe cable 32 and a second opening 104 forming an outlet for the cable32. The arrow indicates the circulation direction of the cable eventhough the detection apparatus functions when the downhole assembly islowered in the well, ie when the cable circulates in a predetermineddirection (unwinding direction), and also when the downhole assembly isremoved from the well, ie when the cable circulates in the oppositedirection (winding direction).

The detection apparatus 100 further comprises a sealing and insulationelement 106, 108 in each opening 102, 104, such as sealing rings, and isfilled with conductive medium 110, such as a conductive fluid, forinstance water. The sealing and insulating elements surround the cableso as to be interposed between the box 101 and the cable 32. They aremade of an electrically insulating material, such as PTFE. Theyelectrically insulate the cable 32 and the box 101 from each other andalso prevent leak from the conductive fluid 110 outside of the box 101.

The detection apparatus 100 also comprise a electrical generator 112connected on one terminal to the box 101 with the interposition of aresistor 113 and on the other terminal to the conductive core of thecable, for instance via the surface unit, in particular via a collectorsituated at the extremity 41A of the cable 32 attached to the drum 37B.The generator may be a voltage or current generator, and generates analternative or continuous signal. It applies a predetermined electricalvoltage and current to the box or the cable so that a voltage differenceis set between the conductive core of the cable and the box. Thedetection apparatus also comprises a electrical measurement device 115,for instance a voltmeter, for measuring a parameter relative to the box101, for instance a potential difference between the box 101 and theconductive core of the cable. It may measure other electrical parameter.However, the value of this parameter when the box is empty correspondsto a predetermined value. For instance, on the embodiment of FIG. 2, themeasured voltage is between the core of the cable and the box but themeasured voltage may be the voltage of the resistor 113.

The box 101 may also be insulated from the ground and the formation 16so that the events happening around the detection apparatus do notinfluence the measurement.

The detection may be performed while a signal is transmitted to thedownhole assembly as the measurement does not generate perturbationsrelative to the transmitted signal.

We will describe below how this apparatus detects the anomalies. Whenthe cable passes in the box and that no anomaly is situated in the box,the conductive core is insulated from the outside by the outer sheath.In this case, as no electrical contact happens between the cable 32 andthe box 101, the electrical circuit formed between the cable 32 and thebox 101 is an open circuit. The electrical parameter then corresponds tothe predetermined value.

However, when a portion of cable with an anomaly enters the detectionapparatus, the conductive core interacts with the box 101 via theconductive fluid and the electrical circuit closes which leads to thecirculation of current in the circuit. The value of the electricalparameter then changes. The magnitude of the anomaly may be measured.Indeed, the bigger the current leak from the cable to the box will be,the greater the change of the electrical parameter will show.

As can be seen on FIG. 3, which is a plot showing a curve 120 of ameasured voltage by the electrical measurement device 115 versus timetaken while a cable comprising different types of anomalies passes inthe box, the measured voltage is set to a default voltage 122 decreasesin portion 124, 126, 128, 130, 132 corresponding to when an anomalypasses in the box. The decrease of the measured voltage varies infunction of the type of anomaly that passes in the box 101. As alreadyindicated above, other electrical parameters such as current,capacitance, impedance, etc. may be measured and enable to obtainsimilar results

FIG. 4 shows an electrical model of the detection apparatus when ananomaly is in the box. The current leak between the box 101 and theconductive core is modelled as the circuit 116 comprising a capacitorand a resistor in parallel. The measured electrical parameter enables tocharacterize this circuit 116 and obtain values of the impedance of theresistor and capacitor depending on the magnitude of the anomalies. Thevalues of the impedances of the resistance and capacitor may also be setto a predetermined value that does not take into account the magnitudeof the anomaly.

The model of FIG. 4 is a simple model that does not take into accountthe elements of the installation situated around the detectionapparatus. However, a more complex model taking into account the otherelements of the installation may be set. One or several filters, such asa low pass filter, may also be provided in the detection apparatus foreliminating undesirable signals that may have an effect on the signalmeasured by the electrical measurement device 115.

In an alternative to the first detection apparatus, the conductive fluidmay be replaced by conductive punctual elements, such as metallic balls.In another variant shown in FIG. 2B, an electrical contact with thecable may be obtained via at least one brush 150 having a metallic pin152 and having metallic bristles 154 arranged so that the bristles arein contact with the cable when the cable is spooled or unspooled. Morespecifically, on FIG. 2B, the arrangement comprises three brushesdisposed so as to surround the cable and to detect the defects on itswhole circumference. They are arranged on a metallic support 156comprising an aperture 158 for enabling the passage of the cable andintegral with the pins 152 of each brush that extend away from thesupport 156. The pins are tilted so that the bristles 154 situated atthe free end of the pin 152 have a contacting zone close to the aperture158 when projected on the support 156, which enables to perform thecontact with the cable. The brush bristles are in flexion on the cable.The support 156 is also provided with an electrically insulating coating160 at the aperture to guide the cable closely while avoiding anyelectrical contact with the support at the level of the aperture 158.Regarding the electrical circuit, the support is connected to the sameelectrical circuit as the box of the apparatus shown on FIG. 2. Thedefect is detected when there is an electrical contact between the brushand the central core of the cable 32, as previously explained.

This variant may be easily integrated at a low cost and is not dependentfrom climatic conditions or from the exact properties of the fluid as inthe first detection apparatus described in FIG. 2. Of course, thearrangement shown on FIG. 2B is exemplary and any arrangement formaintaining at least one brush in contact with the cable is appropriate.

The first detection apparatus may be situated anywhere between the wellhead and the winder so as to provide data regarding the anomalies of thecable 32 each time the cable is wound and/or unwound. It may however besituated in a separate testing facility as well.

A second type of detection apparatus 200 is shown on FIG. 5. Thisdetection apparatus 200 comprises two adjacent cylindrical sealingelements 202, 204 made of a deformable material, such as an elastomer.The sealing elements may be packers for instance. The sealing elements202, 204 are identical. Each of them comprises a central orifice 208,210 for receiving the cable 32 and is configured to hold tight the cableby deforming if the external shape of the cable changes.

The second detection apparatus also comprises a measuring device 206 formeasuring a pressure differential between both sealing elements. Thepressure of the sealing element indeed depends on the shape of the cableas the sealing element expands or retracts to match the cable's externalshape. When an anomaly passes in one of the sealing element, thepressure of the element decreases as it expands to match the shape ofthe sealing element. The differential pressure enables to haveinformation on anomalies on the cable, that may be used as part of thesecond detection apparatus.

The second detection apparatus may include not only two sealing elementsbut three, four or more sealing elements. Further, it may be situated inthe intervention installation, so that the anomalies of the cable 32 aredetected every time the cable is wound or unwound, and in particular inthe stuffing box 44 which already includes such sealing elements forsealing the well. It may also be situated outside of the interventioninstallation.

A third type of detection apparatus 230 is shown on FIG. 5B & FIG. 5C.The third detection apparatus 230 comprises at least an infrared sensor232 for detecting infrared emission of the cable, such as an infraredcamera. In particular the third detection apparatus may comprise aplurality of infrared sensors 232A-232F for surrounding the cable 32 inorder to detect the defects of the cable on its whole circumference. Inthe example shown on FIG. 5C, the apparatus comprises six infraredsensors disposed around the zone for the passage of the cable 32 but anynumber of infrared sensor is appropriate. In order to enhance thedetection, the apparatus may also comprise a heater 234, disposedupstream of the infrared sensor.

As the central core of the cable is made of a metallic material whilethe outer sheath is made with an electrically insulating material, moreparticularly a plastic material, the central core and the outer sheathhave very different thermal conductivities. Therefore, the temperatureof the central core and the temperature of the outer sheath are not thesame. The temperature difference is increased when the cable has beenheated beforehand. Thus, when the cable is damaged and the central coreof the cable 32 is apparent, which constitutes a defect, the infraredsensor show a zone having a different color than the outer sheath of thecable. A simple post-processing of the images sent by the sensors enableto detect the defects in the cable 32.

The method 300 for monitoring performances of the cable will then bedescribed in more details, in reference to FIG. 6.

In a first stage (at box 302), the anomalies of the cable are detectedby the first and/or second detection apparatus or any appropriatedetection apparatus and, if applicable, characteristics of an electricalcircuit modelling the anomaly are estimated. The detection apparatuscommunicates with the processor of the surface control module and thesurface control module associates (at box 304) each detected anomalywith a position of the anomaly on the cable. This may be performed byassociating the data of detection apparatus with time data at thedetection apparatus. Surface control unit 38 also communicates with thewinder that determines the length of unwound cable at each time. Knowingthe installation and the shifting in length between the winder and thedetection apparatus, the position of the cable situated in the detectionapparatus at a predetermined time may be calculated.

Once the position and optionally magnitudes of the anomalies have beenobtained, an electrical model of a configuration of the well isgenerated (box 306). A configuration of the well is taking into accountseveral parameters of the well, for instance the fluids contained in thewell in function of depth. This electrical model may depend on theposition and magnitude of the anomalies and also on the fluids that arecontained in the well. Once the electrical model is generated aparameter relative to the transmitted signal between the surface controlunit 38 and the downhole assembly 30 is determined (at box 308). Thetransmitted signal may be for instance plotted for each depth at whichthe downhole assembly 30 is set. The parameter may be the transmittedsignal itself or lost signal.

The method may also comprise after obtaining the signal loss, predictingif a job in the predetermined configuration will succeed and, if not,recommending appropriate action for ensuring the job success (at box311)

An example of an electrical model is shown on FIG. 7. The drum 37B ismodelled by a coil whose inductance is set in function of the length ofwound cable around the drum. The core of the cable 32 is modelled as aresistor having a known impedance while the duct 22 and surface unit 38are modelled as connected to the electrical mass. The electricalconnection between the core of the cable and the casing is modelled as acapacitor 309. Further, the anomalies 310, 312 are modelled at theirassociated position as a circuit comprising a resistor 310B, 312B and acapacitor 310A, 312A in parallel. In the model shown on FIG. 7, only twoanomalies have been detected on the cable but of course, the model maycomprise as many modelled RC circuits as there is anomalies. Themodelling of the anomalies and/or of the installation is not limited tothe model set here. Other more or less complex models may be used aswell.

The value of the impedance and capacitance of these modelled resistors310B, 312B and capacitors 310A, 312A may be set at a predetermined valueif the detection apparatus is not able to determine the magnitude of theanomaly. Alternatively, it may depend on the magnitude of the anomalythat has been detected. For instance, the value of the impedance and ofthe capacitance of the modelled circuit match the ones that have beendetermined with the first detection apparatus.

In another embodiment, the values of the impedance and capacitance ofthese modelled resistors 310B, 312B and capacitors 310A, 312A may dependon the fluid situated in the wellbore at the position of the anomaly.Indeed, the impedance of the resistor modelling the anomaly will not beidentical if the anomaly is situated in water or oil. In this case, themethod may comprise determining the fluids in presence in the wellboreat the position of each anomaly (at box 314) and calculating theimpedance and capacitance of the modelled resistors 310B, 312B andcapacitors 310A, 312A on the basis of the fluid that is situated at thisposition (at box 316). This may be performed for instance by determiningthe resistivity of the fluid in the well and determining the resistivityof the fluid in the conductive box and to estimate the value of theimpedance of the resistor and the capacitance of the capacitor on thebasis of the measured values in the first detection apparatus and of theresistivity of the fluids in the detection apparatus and in thewellbore. Alternatively, if the fluid in the wellbore is not known, thevalues of the impedance of the resistor and the capacitance of thecapacitor may be determined as if the fluid in the wellbore was a veryconductive fluid, such as brine or saline water, that would generategreater losses of signals. Once the values has been estimated, theelectrical model may be set (at box 318).

For facilitating the determination of the values of the impedance of theresistors 310B, 312B and of the capacitance of the capacitor 310A, 312A,the method may also comprise a calibration of the first detectionapparatus. This calibration comprises inserting in the conductive box ofthe first detection apparatus a predetermined sample of a cable andmeasuring its associated electrical parameter. This measurement may thenbe compared to the same measurement made in a reference fluid. Acorrective factor may then be determined for the values of the impedanceand capacitance as determined in the first detection apparatus comparedto the values determined in the reference fluid. This calibrationenables to have consistent model regardless of the used conductive fluidin the first detection apparatus. Further, fluids situated in the wellmay also be solely compared to the reference fluid in this case.

FIG. 8 shows a plot 400 of an transmitted signal in function of depth ofthe downhole assembly estimated thanks to the above-mentioned electricalmodel (shown on curve 402) for a predetermined cable in a predeterminedconfiguration of the well. The curves 404 and 406 show respectively thetelemetry signal up from the downhole assembly to the surface and thetelemetry signal down from the surface control module to the downholeassembly that was measured at each depth of the downhole assembly whenthe predetermined cable was set in the well in the predeterminedconfiguration. It shows the method according to the disclosure isconsistent and enables to predict the success or failure of a next job.

The prediction may be based on the comparison of the signal obtained atthe depth at which the job is performed with a predetermined thresholdvalue. It will be predicted that the job will fail if the level of thesignal is below the threshold. In this case, the recommendation may beto cut the cable at its free end so as to throw away a certain length ofcable as the cable that has not been unwound and used is considered asundamaged. An electrical model of installation with the cable cut at itsfree end may be generated based on the acquired data by the detectionapparatus so as to simulate the signal transmitted by such a cable, inorder to guarantee an efficient decision-making. Another recommendationmay be to change the cable for instance if the remaining length of thecable once the damaged portion at its free end has been removed isinferior to the depth of the job to perform.

The deformation in length of the cable may also be monitored in order toobtain additional data relative to the performances of the cable. Thismay be performed without any additional device by comparing the positionof a detected anomaly on a cable during a first detection operation andthe position of the same anomaly during a second detection operationtaking place later during the life of the cable. Indeed, if the positionof the anomaly has changed relative to a reference position (forinstance the end 41B of the cable), it shows that the cable hasundergone a deformation such as a lengthening. When the detectionapparatus for detecting the anomaly is situated on the interventioninstallation, the comparison may be performed between detectionoperation done both when winding or both when unwinding the cable.Indeed, there may be an elastic and reversible lengthening of the cableto be wound because of the weight of the downhole assembly that exerts atension at the end of the cable and the results may be interpreted moreeasily by comparing detection operations performed at the same stage ofthe well intervention.

It may also be monitored with an additional device comprising a markerthat marks the cable for instance setting the marks at predeterminedpositions on the cable, such as every 20 meters. The additional devicemay also comprise a detector for detecting the marks and associatingthem with a position on the cable. This may also allow to monitor thelengthening of the cable over time. The marker may be an apparatus forspraying or coating the cable with cobalt and the detector may be agamma-ray detector able to detect the cobalt.

Additional monitoring may also comprise an optical device, such as aLASER for determining the cross-section of the cable, which may enableto detect local anomalies as well as lengthening of the cable, that maybe related to a decrease of the diameter of the cable.

Such monitoring enables to obtain information about the state of thecable and to avoid using the cable for a job if the cable is not able tocorrectly perform the job, on an electrical and/or mechanicalstandpoint.

Another aspect of the disclosure is to prevent the cable from beingdamaged so that the number of jobs it performs may significantlyincrease. It has been demonstrated that the cable was mainly damagedduring the winding and unwinding and that an optimal distribution of thecable on the drum ensure less damages on the cable while winding andunwinding.

Spooling sleeves for fitting around drums comprising grooves for guidingthe first layer of the cable on the drum already exist and improve thespooling operation. Manufacturing dimensional uncertainties of the drumand sleeve may create gaps between the sleeve and flanges of the drumleading to difficulties to perform the spooling correctly.

The disclosure also relates to spooling sleeves. As previouslydisclosed, spooling sleeves 500, 600, 700 have a generally cylindricalshape and are configured to fit around a spooling drum. They may be madeof a flexible material and may be made of two half-cylinders 502, 504;602, 604; 702, 704 cut according to a surface P containing the axis ofthe cylinder. The half cylinders may also be rotatably mounted relativeto each other via an axis parallel to the axis of the cylinder between afirst position in which they are at least partly separated to receivethe drum between the half-cylinders and a second position in which thehalf-cylinders are closed around the drum so that an internal surface ofthe sleeve tightly fit the external surface of the drum (not representedon the drawings).

The first spooling sleeve 500 according to the disclosure is shown onFIG. 9 and comprises a first portion 506 comprising helical grooves 507extending around the periphery of the drum. The grooves 507 may bearranged as disclosed in U.S. Pat. No. 3,391,443 or in any appropriatemanner. The first portion 506 extends on at least 80%, in particular90%, of the peripheral surface of the sleeve.

It also comprises a second portion 508 situated at one longitudinal endof the sleeve and devoid of grooves. This second portion enables tohandle the manufacturing dimensional uncertainties. Indeed, as shown onFIG. 10, representative of the sleeve fitted on a drum 512 comprisingflanges 514, 516 at both of its longitudinal ends, due to suchmanufacturing dimensional uncertainties, the drum may be slightly longerthan expected which may create a gap 517 between the flange and thesleeve and then the last turn of cable that may endanger the spooling ofthe cable 32. As the second portion is devoid of grooves, it enables tohandle more freedom in the positioning of the cable in this portion andto handle such gap by positioning it between two turns of cable (asshown at 518) and also optionally to distribute the gap betweendifferent turns of cable 32, for instance between the first and secondturn, and the second and third turn, which has not been shown in FIG.10.

A second spooling sleeve as shown on FIG. 11 also comprises twohalf-cylinders 602, 604, but each of this half-cylinders comprises twoindependent parts 606, 608; 610, 612, having each a half-cylinder shapeas well. The parts 606, 608 and 610, 612 have complementary shapes inorder to respectively form half-cylinders 602, 604.

Each part comprises a first portion 614, 616, 618, 620 situated at afirst longitudinal end of the part forming as well a longitudinal end ofthe sleeve and comprising peripheral grooves for spooling the cable 32around the drum as already in reference to the first spooling sleeve500.

Each part also comprises a second portion devoid of grooves,respectively 620, 622, 624, 626. These portions are situated at a secondlongitudinal end of the part 606, 608, 610, 612 and form together a zoneof the sleeve situated in the center of the sleeve once assembled,relative to the longitudinal axis, so that it is situated between thefirst portions 606, 610 on one side of the sleeve and first portions608, 612 on the other side of the sleeve.

The longitudinal attachment edges of each of the second portions 620,622 and 624, 626 are of complementary shape. Their edge 626, 628 is cutin a specific pattern, such as a zigzag pattern as shown on FIG. 11.This pattern is chosen so that the length of the edge portions having atangent situated in a predetermined plan perpendicular to the axis ofthe cylinder are less than 20% of the perimeter of the sleeve. Asinusoidal pattern, a rectilinear pattern tilted relative to the planperpendicular to the axis of the sleeve or a stepping patterns havingdifferent plateau in different plans, the total length of the plateauxsituated in one predetermined plan not exceeding 20% of the perimeter ofthe sleeve, may also be chosen.

As the previous one, such sleeve enables to handle the manufacturingdimensional uncertainties of the drum 512. These uncertainties maygenerate a gap 630 between the edges 626, 628 of the parts 606, 608, asshow on FIG. 12. But as the pattern of the edges is chosen so that edgeportions having a tangent situated in a predetermined plan perpendicularto the axis of the cylinder are less than 20% of the perimeter of thesleeve, the gap has the same shape and the cable does not get stuck inthe gap even if its dimension in the axial direction of the sleeve is ofthe same order as the diameter of the cable.

Further, this sleeve enables to position correctly the cable 32 next tothe flanges 514, 516 of the drum 512, as grooves 617 guiding the cable32 are present at both ends of the sleeve. In the central zone of thesleeve, made of the adjacent second portions 620, 622 and 624, 626, thefreedom to position the cable 32 is greater and the gap due tomanufacture dimensional uncertainties may be distributed between thecable turns surrounding the second portion as shown at 632, which mayensure a correct spooling of the subsequent layers even taking intoaccount the manufacturing uncertainties. This distribution may beperformed, for instance manually, after the first spooling of the firstlayer of the cable 32 around the drum.

As shown on FIG. 13, each half cylinder 702, 704 of the sleeve 700 maynot be made of two independent parts but for instance of threeindependent parts 710, 712, 714, so as the sleeve comprise two distinctcentral zones devoid of groove 716, 718 instead of one. It may alsocomprise any number of independent parts. The edges of the secondportions of each of the parts are however cut in a zigzag pattern asexplained above. It enables to further distribute the gap due to thedimensional uncertainties in two zones of the sleeve and to decrease thedimensional of each of the gaps.

The percentage of the periphery of the sleeve being devoid of groovesmay be inferior to 50%, more particularly to 20%.

In view of the entirety of the present disclosure, including thefigures, a person skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same uses and/orachieving the same aspects introduced herein. A person skilled in theart should also realize that such equivalent constructions do not departfrom the spirit and scope of the present disclosure, and that they maymake various changes, substitutions and alterations herein withoutdeparting from the spirit and scope of the present disclosure. Forexample, although the preceding description has been described hereinwith reference to particular means, materials and embodiments, it is notintended to be limited to the particulars disclosed herein; rather, itextends to functionally equivalent structures, methods, and uses, suchas are within the scope of the appended claims.

The disclosure relates in particular to a method for monitoring theperformances of a cable for carrying a downhole assembly in a wellbore,the cable comprising at least a conductive core and an insulating outerlayer, the method comprising:

-   -   Performing on at least a portion of the cable a detection        operation for detecting the presence of at least a local anomaly        on the cable;    -   Generating an electrical model of a predetermined configuration        of an installation including the cable and the downhole assembly        disposed in the wellbore, the model being defined in function of        the detected local anomalies,    -   Estimating a parameter relative to a signal transmitted by the        cable between the downhole assembly and a surface equipment in        the predetermined configuration on the basis of the electrical        model.

The parameter relative to a signal transmitted may be the signaltransmitted itself or a signal lost between the surface and the downholeassembly.

The detection operation may be performed while lowering and/or removingthe downhole assembly from the wellbore. Performing the detectionoperation may then comprise passing the portion of the cable by adetection apparatus while lowering and/or removing the downhole assemblyfrom the wellbore In this case, while performing a job, the data forestimating a later job may be gathered. It may also be performed outsideof an intervention installation.

In one embodiment, the detection apparatus comprises a conductiveelement in contact with the cable, performing the detection operationcomprising applying a voltage difference between the element and thecable and measuring an electrical parameter relative to the element. Forinstance, the conductive element is a box filled with a conductivemedium, and performing the detection operation comprises applying avoltage difference between the box and the cable and measuring anelectrical parameter relative to the box. The conductive medium may be aconductive fluid or a plurality of conductive elements such as balls.The box may be insulated from the formation. Similarly, the conductiveelement may be a brush having metallic bristles contacting the cable.

In another embodiment, the detection apparatus comprises at least twopressurized sealing rings for surrounding the cable, and performing thedetection operation comprises measuring a pressure differential betweenthe sealing rings. This detection apparatus may be situated inparticular in the stuffing box as the stuffing box comprises sealingelements for insulating the wellbore from the surface.

In another embodiment, the detection apparatus may comprise at least aninfrared sensor for detecting the infrared emission of the cable. It mayadditionally comprise a heater situated upstream from the infraredsensor.

The method may be performed with data coming from one or severaldetection apparatuses. Further, any detection apparatus enabling todetect an anomaly, such as a dimensional measurement apparatus, forinstance LASER, may be used for performing the method.

The method may also comprise associating the anomaly with a position onthe cable.

It may also comprise performing a first detection operation at a firsttime and a second detection operation at a later time, comparing theresults of the first and second detection operation and determining aparameter relative to the length of the cable on the basis of thecomparison. This parameter may be an elastic or plastic deformation ofthe cable.

Performing the detection operation may also comprise determining amagnitude of an anomaly. An anomaly may be a hole or a crack in theinsulation layer or coating of the cable and the magnitude is related tothe dimension of the anomaly and in particular to how it affects thesignal transmitted from the surface equipment to the downhole assembly.

The electrical model of the predetermined configuration of theinstallation is designated wellbore electrical model, and whereinperforming the detection operation comprises generating an electricalmodel of the detection apparatus, designated anomaly electrical model,and estimating electrical characteristics of an first electrical circuitmodelling the local anomaly, wherein generating the wellbore electricalmodel comprises modelling the anomaly with a second electrical circuithaving electrical characteristics determined on the basis of theelectrical characteristics of the first electrical circuit. Theelectrical characteristics may be impedance, capacitance or inductanceof the components of the electrical circuit modelling the anomaly. Theelectrical circuit may be in particular a RC circuit, ie a resistor anda capacitor in parallel.

In an embodiment, first and second electrical circuits may have sameidentical characteristics.

In another embodiment, the wellbore electrical model is defined infunction of at least a property of a fluid present in the wellbore inthe predetermined configuration of the installation. In particular, theelectrical characteristics of the second electrical circuit aredetermined based on the electrical characteristics of the first circuitand on the property of the fluid. The considered property of the fluidmay be the resistivity.

The method may also comprise calibrating the detection apparatus bymeasuring an electrical parameter relative to the element, in particularthe box, when a predetermined sample is in the detection apparatus,wherein performing the detection operation comprises normalizing themeasured electrical parameter relative to a reference detectionapparatus. The reference detection apparatus may for instance be filledwith a reference fluid.

The cable may be a wireline cable or a slickline cable.

The method comprises predicting, on the basis of parameter relative tothe transmitted signal, a potential failure of the cable in thepredetermined configuration of the installation.

The method comprises recommending an optimized configuration of thecable when the failure of the cable is predicted. The optimizedconfiguration may be determined based on the parameter relative to thetransmitted signal and on the length of the cable.

The method comprises monitoring a dimensional parameter of the cable(via LASER, cobalt marking) on the portion of the cable in addition andpredicting the cable failure on the basis of the dimensional parameteras well.

The disclosure relates to a system for monitoring the performances of acable for carrying a downhole assembly in a wellbore and comprising atleast a conductive core and an insulating outer layer, the systemcomprising:

-   -   a detection apparatus for detecting the presence of at least a        local anomaly on the cable;    -   a processor for:        -   i. Generating an electrical model of a predetermined            configuration of an installation including the cable and the            downhole assembly disposed in the wellbore, the model being            defined in function of the detected local anomalies,        -   ii. Determining a parameter relative to the signal            transmitted by the cable between the downhole assembly and a            surface equipment of the installation in the predetermined            configuration on the basis of the electrical model.

The system may comprise a device for lowering the downhole assembly inthe wellbore and/or removing the downhole assembly from the wellbore,configured so that the cable passes by the detection apparatus when thedownhole assembly is lowered and/or removed from the well.

The detection apparatus may be installed in a stuffing box of the systemfor lowering and/or removing the downhole assembly.

The disclosure also relates to a sleeve for spooling a cable around adrum, having an essentially cylindrical shape of a predetermined axisand configured to be disposed around a spooling surface of the drum, thesleeve comprising at least two independent parts, each part forming atleast a fraction of an essentially cylindrical shape and having atleast:

-   -   A first portion, comprising at least a peripheral groove to        receive the cable,    -   A second portion situated at least at one of the longitudinal        ends of the part and having a longitudinal attachment edge,        wherein the attachment edges are configured so that a        longitudinal attachment edge of a first part is of complementary        shape of a longitudinal attachment edge of a second part,        wherein the attachment edges comprise at least an edge portion,        and are each configured so that the total length of the edge        portions having a tangent situated in a predetermined plan        perpendicular to the axis of the cylinder are less than 20% of        the perimeter of the sleeve.

The parts may be arranged so that the sleeve comprise in thelongitudinal direction a first zone at each of its end, and at least acentral zone being formed by two adjacent second portions of the firstand second parts of the sleeve.

The attachment edges may have:

-   -   A zigzag shape    -   A sinusoidal shape    -   A rectilinear shape tilted in a plan having a normal line tilted        relative to the axis of the sleeve)

The invention claimed is:
 1. A method for monitoring the performances ofa cable for carrying a downhole assembly in a wellbore, the cablecomprising at least a conductive core and an insulating outer layer, themethod comprising: Performing on at least a portion of the cable adetection operation for detecting the presence of at least a localanomaly of the cable, wherein performing the detection operationcomprises passing the portion of the cable by a detection apparatuswhile lowering and/or removing the downhole assembly from the wellbore;Generating an electrical model of a predetermined configuration of aninstallation including the cable and the downhole assembly disposed inthe wellbore, the model being defined as a function of the detectedlocal anomalies, Estimating a parameter relative to a signal loss due tothe detected local anomalies in a signal transmitted by the cablebetween the downhole assembly and a surface equipment in thepredetermined configuration on the basis of the electrical model.
 2. Themethod according to claim 1, wherein the detection apparatus comprises aconductive element, and performing the detection operation comprisesapplying a voltage difference between the conductive element and thecable and measuring an electrical parameter relative to the conductiveelement.
 3. The method according to claim 2, wherein the conductiveelement is a box filled with a conductive medium.
 4. The methodaccording to claim 2, wherein the conductive element is a brush havingmetallic bristles.
 5. The method according to claim 1, wherein thedetection apparatus comprises at least two pressurized sealing rings forsurrounding the cable, and performing the detection operation comprisesmeasuring a pressure differential between the sealing rings.
 6. Themethod according to claim 1, wherein the detection apparatus comprisesat least one infrared sensor for detecting the infrared emission of thecable.
 7. The method according to claim 1, comprising associating theanomaly with a position on the cable.
 8. The method according to claim7, comprising performing a first detection operation at a first time anda second detection operation at a later time, comparing the results ofthe first and second detection operation and determining a parameterrelative to the length of the cable on the basis of the comparison. 9.The method according to claim 1, wherein performing the detectionoperation comprises determining a magnitude of an anomaly.
 10. Themethod according to claim 1, wherein the electrical model of thepredetermined configuration of the installation is designated wellboreelectrical model, and wherein performing the detection operationcomprises: generating an electrical model of the detection apparatus,designated anomaly electrical model, wherein the anomaly electricalmodel models the detection apparatus and the portion of cable situatedtherein, and based on the anomaly electrical model and the detectionoperation, estimating at least an electrical characteristic of a firstelectrical circuit modelling the local anomaly in the detectionapparatus, wherein generating the wellbore electrical model comprisesmodelling the anomaly with a second electrical circuit having at leastan electrical characteristic determined on the basis of the at least oneelectrical characteristic of the first electrical circuit and of one ormore properties of the wellbore, wherein the anomaly is modelled at anexpected position in the predetermined configuration of theinstallation.
 11. The method according to claim 1, wherein the wellboreelectrical model is defined in function of at least a property of afluid present in the wellbore in the predetermined configuration of theinstallation.
 12. The method according to claim 2, comprisingcalibrating the detection apparatus by measuring an electrical parameterrelative to the element when a predetermined sample is in the detectionapparatus, wherein performing the detection operation comprisesnormalizing the measured electrical parameter relative to a referencedetection apparatus.
 13. The method according to claim 1, wherein thecable is a wireline cable or a slickline cable.
 14. The method accordingto claim 1, comprising predicting, on the basis of parameter relative tothe transmitted signal, a potential failure of the cable in thepredetermined configuration of the installation.
 15. The methodaccording to claim 10, wherein the at least one electricalcharacteristic includes at least one of an impedance and a capacitance.16. The method according to claim 10, wherein the detection apparatuscomprises a conductive element, and performing the detection operationcomprises applying a voltage difference between the conductive elementand the cable and measuring an electrical parameter relative to theconductive element, wherein the at least one electrical characteristicof the first circuit depends on the local anomaly and one or moreproperties of the detection apparatus, wherein the one or moreproperties of the detection apparatus and the one or more properties ofthe wellbore are compared to one or more reference properties in orderto determine the electrical characteristic of the second circuit. 17.The method according to claim 16, wherein the one or more properties ofthe wellbore include a composition of a fluid situated in the wellbore.18. A system for monitoring the performances of a cable for carrying adownhole assembly in a wellbore and comprising at least a conductivecore and an insulating outer layer, the system comprising: a detectionapparatus for detecting the presence of at least a local anomaly of thecable; a device for lowering the downhole assembly in the wellboreand/or removing the downhole assembly from the wellbore, configured sothat the cable passes by the detection apparatus when the downholeassembly is lowered and/or removed from the well, a processor for: i.Generating an electrical model of a predetermined configuration of aninstallation including the cable and the downhole assembly disposed inthe wellbore, the model being defined as a function of the detectedlocal anomalies, ii. Determining a parameter relative to a signal lossdue to the detected local anomalies in a signal transmitted by the cablebetween the downhole assembly and a surface equipment of theinstallation in the predetermined configuration on the basis of theelectrical model.